1. Field of the Invention
This invention relates to systems for storing organic liquids such as fuel oil and the like, and especially to such systems which are adapted to ensure that the organic liquid is not accidentally allowed to escape into and contaminate the environment.
2. Discussion of Related Art
Fuel oil storage facilities customarily comprise a number of tanks in which fuel oil is contained. Occasionally, leaks occur which allow the stored fuel oil to escape into the surrounding environment. If such a leak goes undetected, relatively severe environmental damage to, for example, ground water may occur. Consequently, it is desirable to provide a secondary containment structure around each tank in order to trap any escaping fuel oil.
One type of structure which is useful to contain escaping fuel oil is a wall or dike erected to form a moat around an associated storage tank. However, a problem which arises with such a moat is that water, e.g., rain, condensation and the like, can accumulate in the moat, thereby reducing its capacity for holding fuel oil in the event of a leak.
Accordingly, it is necessary to provide a mechanism which will allow water to drain freely from the moat yet will retain any leaked fuel oil in the containment area.
Several valving mechanisms for separating fluids of varying densities have been suggested. Huiet, Jr., U.S. Pat. No. 4,051,030, and Moyer, U.S. Pat. No. 3,115,888, disclose float valves with floats having a density intermediate oil and water located above the valve inlet opening. The float of Huiet acts as a seal for the outlet at the bottom of the float chamber while the float of Moyer is located at the end of a pivot arm which operates a butterfly valve in the outlet line. However, the valves disclosed in each of these references are designed to be located in a sump at the bottom of an oil tank and are not adapted for use in a moat surrounding such a tank.
Olsen, U.S. Pat. No. 3,745,115, shows an oil and water separating chamber provided with two valves operated by floats which float at the interphase between the oil and the water in the separation chamber. One of the valves is a slide valve having an opening below the level of the float which allows water to escape from the bottom of the chamber. The other valve is a pivot valve having an opening above the level of the float which allows oil to escape from the top of the chamber. Again, this device is not adapted for use in a moat surrounding a storage tank.
McKee, U.S. Pat. No. 3,675,771, discloses a water surge tank with a floating drain line which maintains a constant layer of oil on top of water with float operated switches for starting and stopping the flow of water out of the tank so that the water level is constantly raised and lowered in the tank. This mechanism also does not lend itself to use with a moat surrounding a storage tank in that it allows a significant amount of water to remain unpurged.